a) Field of the invention:
The present invention relates to an optical system for monitor cameras to be mounted on vehicles, and more specifically to an optical system for monitor cameras which are to be mounted on vehicles for detecting the presence of obstacles located within ranges of visual fields at dead angles.
b) Description of the prior art:
In the field of sideway monitors for vehicles, there is known, for example, a monitor disclosed by Japanese Patent Kokai Publication No. Sho 57-33,045. This monitor comprises a camera body which is mounted on a bonnet of a vehicles so as to be freely rotatable for permitting detection of securities on the right and left sides of the vehicle in cases, for example, where the vehicle is to run into a road from a place at which a driver cannot have good visibilities on the right and left side of the vehicle.
However, the monitor disclosed by the Japanese Patent Kokai Publication No. Sho 57-33,045 has a section which is relatively long as measured from the camera body to a driver's seat and provides narrow visual fields, thereby permitting confirmation of securities within narrow visual fields.
In the field of monitors for detecting securities within ranges at the back of vehicles, there is known a monitor which is disclosed by Japanese Utility Model Kokai Publication No. Sho 60-119,179. This monitor is configured so as to permit monitoring securities by using a monitor TV which is equipped with the TV camera disposed in the vicinity of a driver's seat.
In the case of the sideway monitor for vehicles, obstacles which are present near road surfaces often hinder confirmation of securities. Accordingly, it has been proposed to dispose a monitor camera, such as a video camera at a location which is higher to a certain degree than the road surfaces as schematically illustrated in FIG. 1. The sideway monitor shown in FIG. 1 uses a video camera 3 which is mounted on a support 2 erected on a portion of a vehicle body 1.
However, this sideway monitor is problematic in that it is disadvantageous for accommodation while it is unused and in that it is rather fragile against external impact.